On Jul 26, 2016, at 8:49 AM, Jorge . <chocolate.camera@gmail.com> wrote:

When placing a black-and-white photograph in a page that will also have plenty of other photographs, illustrations and layout elements in color, part of a magazine that will be printed in offset, is there a rationale for preferring that gray values of that photograph are printed using only black ink or with a mix of all CMYK inks instead?

That will depend in no small amount on the particular press and its inkset -- and quite possibly the paper as well. For what it's worth, many modern fine art inkjet printers use some mix of all their inks when printing grayscale images. Big considerations..."black" inks are never actually spectrally flat, though quality ones are sometimes "good enough." That would drive you towards an ICC profile that balances out the color of the black ink -- especially if the paper stock is itself non-neutral (because you'd want to shift the black ink towards the tint of the paper). But, on the flip side, if you've only got a CMYK printer, that might suggest a relatively low frequency screening pattern, in which case the individual halftone dots might be visible in an objectionable way. And on the gripping hand, the multiple inks can have a similar effect as sub-pixel antialiasing on LCD displays and help give the perception of higher-than-you-really-have resolution. Short answer? Make some test prints and judge for yourself. Cheers, b&

On 26 Jul 2016, at 16:49, Jorge . <chocolate.camera@gmail.com> wrote:

The particular CMYK combination I mean is the one I would automatically get in the likes of Photoshop by converting the grayscale image to the target CMYK color space using ICC profiles.

Jorge If your B&W image is small on the page then you can convert it to CMYK using whatever ICC profile the magazine suggests and there won’t be a problem. As the B&W image gets bigger and more significant then a conventional CMYK ICC profile will be a problem— in fact it is very likely to be rejected by magazines if you are submitting advertising repro. The conventional ICC CMYK profile uses far too much CMY for neutrals. If grey balance poor then your B&W single page may not meet your expectations. If grey balance is just slightly less than perfect then you may see differences between the left and right pages of double page spreads. It’s too tough a test for the printer, so you should avoid risking it. There are some GCR variants of common profiles available on the web. I know that BasICColor provide them and they’d work well. Pro shops usually build their own high GCR profiles or use non-ICC systems whose primary purpose is saving money through ink limiting. It’s worth getting a microscope on your favourite magazines and taking a closer look at those black dots. There’s a lot more K than most people expect and a lot more intervention than many expect — including advertising content on some titles. Regards -- Martin Orpen Idea Digital Imaging Ltd